The present invention relates to a method for coating an end face of a high-output semiconductor laser for use in CD-R/RW or the like by electron beam deposition wherein the film thickness is adjusted upon the end-face coating, and a fixing frame used in this method.
Conventionally, electron beam deposition has been employed as a method for coating an end face of a semiconductor laser.
However, with an increased demand for semiconductor lasers for use in communication, storage and so forth in recent years, it is becoming necessary to improve work efficiency by coating a large number of semiconductor lasers in one work when the end faces, which are cleavage faces, are coated before manufacturing as a product.
Accordingly, a method of arranging a large number of semiconductor lasers at once in an electron beam deposition apparatus is employed to improve work efficiency. For example, a method has been adopted wherein end faces of a plurality of semiconductor lasers are placed on each of coat batches arranged in a mxc3x97n matrix composed of m vertical columns and n horizontal rows.
As described above, work efficiency of end-face coating can be improved by the method of coating end faces by arranging a large number of semiconductor end faces at once.
However, a problem of this end-face coating by electron beam deposition is that, when a large number of end faces are coated at once, differences in incident angles of a deposition beam to coat batches become large, thereby resulting in thickness variations of deposited films after completion of the deposition.
Such thickness variations of the deposited films result in reflectance variations of semiconductor end faces after completion of deposition thereon as shown in the relationship between the end-face coating film thickness and reflectance when Al2O3 is used as a deposition material in FIG. 1. Such reflectance variations substantially affect characteristics of the semiconductor lasers.
For example, it is known that, in a high-output semiconductor laser, an emission lifetime becomes short when the reflectance of an end face (laser-emitting face) is high, while a so-called SCOOP (Self Coupled Optical Pickup) defect occurs when the reflectance is low. Therefore, when an end face of a semiconductor laser is coated, the reflectance of the end face after completion of deposition needs to match a predetermined reflectance (usually, about 13xc2x12%). FIG. 2 shows reflectance variations after deposition at positions at which semiconductor end faces are disposed. In this figure, the reflectance of a semiconductor laser constituting a coat batch E in the center of the second row is out of the predetermined reflectance range. Therefore, this semiconductor laser cannot be used as a product and thus the industrial demand for a high G/W yield cannot be met.
Accordingly, the object of the present invention is to provide a method for ensuring a higher G/W yield by regulating reflectance variations of all semiconductor lasers arranged in an electron beam deposition apparatus after completion of deposition when end faces of the semiconductor lasers are coated.
In order to achieve the above object, there is provided a method for coating a semiconductor laser end face with a coating material by electron beam deposition by disposing a plurality of coat batches each constituted by semiconductor laser end faces on an array face having a central axis of a deposition beam as a normal line, wherein
the coat batches are disposed at positions in the same distances from a position opposed to the center of the deposition beam on the array face.
In this constitution, since coat batches are positioned at an equal distance from a position opposed to the central axis of a deposition beam emitted from a deposition source on the array face, incident angles of this deposition beam to the respective coat batches are almost equal.
Furthermore, when the incident angles to the end faces are almost equal, the amounts of a coat material deposited through a unit area per a unit time are also almost equal, thereby preventing film thickness variations of the deposited films.
Also, there is provided a method for coating a semiconductor laser end face with a coating material by electron beam deposition by disposing a plurality of coat batches each constituted by semiconductor laser end faces on an array face having a central axis of a deposition beam as a normal line, wherein
an angle-adjusting step for adjusting an incident angle xcex1, xcex2 of the deposition beams to the coat batches is included so that thicknesses of films formed by the deposition beam on the coat batches should be within a predetermined range.
In this constitution, since the incident angles to the respective coat batches are adjusted so that the thicknesses of films formed by the deposition beam on the respective coat batches arranged on the array face should be within the predetermined range, the reflectance affected by the deposition film formed on each coat batch is also within the predetermined range, thereby causing no reflectance variations after formation of the deposition films due to the difference in positions in the electron beam deposition apparatus.
Also, there is provided a method for coating a semiconductor laser end face with a coating material by electron beam deposition by disposing a plurality of coat batches each constituted by semiconductor laser end faces on an array face having a central axis of a deposition beam as a normal line, wherein
when an incident angle of a deposition beam to a coat batch positioned on the array face at a position opposed to the central axis of the deposition beam is assumed as a first incident angle and an incident angle of a deposition beam to a coat batch that is the largest incident angle of the deposition beam on the array face is assumed as a second incident angle,
an angle-adjusting step for adjusting at least the first incident angle so that the angle difference between the first and second incident angles xcex2, xcex1 should be within a predetermined range.
In this constitution, since the angle adjustment step for adjusting the first incident angle is performed so that the angle difference between the first and second incident angles should be decreased to the predetermined range, the difference in the deposition amounts due to the difference in incident angles in a unit area per a unit time is also decreased, thereby preventing film thickness variations on coat batches after completion of deposition.
Also, there is provided a fixing frame in which a plurality of bar arranging jigs for housing a plurality of laser bars so that their respective end faces should face in the same direction when the semiconductor laser end faces are coated by electron beam deposition, wherein
an adjustment mechanism is provided to adjust an angle of each bar arranging jig with an array face assuming the central axis of the deposition beam in a fixing frame as a normal line.
In this constitution, since a fixing frame arranged on the array face assuming the central axis of the deposition beam as a normal line has an adjustment mechanism for adjusting an angle between this array face of the fixing frame and the array face of the bar arranging jig housing a plurality of laser bars, the incident angles of the deposition beam to the end faces of the semiconductor lasers disposed in this fixing frame are adjusted in the fixing frame.